package com.java.multipledatasource.algorithm;

/**
 * @author hu
 * @version 1.0
 * @date 2021/1/20 0020 下午 1:59
 * @description
 */
public class Sort {
    public static void mergeSort1(int[] arr) {
        if (arr == null || arr.length < 2) {
            return;
        }
        process(arr, 0, arr.length - 1);
    }

    public static void process(int[] arr, int L, int R) {
        if (L == R) {
            return;
        }
        int mid = L + ((R - L) >> 1);
        process(arr, L, mid );
        process(arr, mid + 1, R );
        merge(arr, L, mid, R);

    }

    public static void merge(int[] arr, int L, int M, int R) {
        int[] help  = new int[R - L + 1];
        int i = 0;
        int p1 = L;
        int p2 = M + 1;

        while (p1 <= M && p2 <= R){
            help[i++] = arr[p1] <= arr[p2] ? arr[p1++] : arr[p2++];
        }
        while (p1 <= M){
            help[i++] = arr[p1++];
        }
        while (p2 <= R) {
            help[i++] = arr[p2++];
        }
        for (int i1 = 0; i1 < help.length; i1++) {
            arr[i1 + L] = help[i1];
        }
    }

    public static void main(String[] args) {
        int[] arr = {1,2,3,7,5,3,8,9};
        mergeSort1(arr);
        for (int i : arr) {
            System.out.println(i);
        }
    }
}
